1. Field of the Invention
This invention relates to a novel shape selective metal catalyst, a method of preparing same and its employment in various catalytic processes.
2. Description of the Prior Art
Shape selective catalysis utilizing molecular sieves was first demonstrated by P. B. Weisz and V. J. Frilette in J./Phys. Chem. 64, p. 302 (1960). Since then, the shape selective catalytic properties of various zeolites have been extensively demonstrated. For example, N. Y. Chen and W. E. Garwood in "Some Catalytic Properties of ZSM-5, a New Shape Selective Zeolite", Journal of Catalysis, 52, p. 453-458 (1978) described the shape selectivity of ZSM-5. On the other hand, the use of zeolites as shape-selective supports for catalytic functions has received much less attention.
P. B. Weisz, V. J. Frilette, R. W. Maatman and F. B. Mower in "Catalysis by Crystalline Aluminosilicates II. Molecular-Shape Reactions", Journal of Catalysis, 1, p. 307-312 (1962) described a shape selective olefin hydrogenation catalyst comprising platinum incorporated in zeolite A. In U.S. Pat. No. 3,140,322 of V. J. Frilette and P. B. Weisz, a process is disclosed for hydrogenation using a platinum containing zeolite. In U.S. Pat. No. 3,226,339 of V. J. Frilette and R. W. Maatman, a process is described for the preparation of a platinum or palladium containing zeolite catalysts. U.S. Pat. No. 3,575,045 of J. N. Miale discloses the use of a platinum entrained zeolite A for selective hydrogenation.
A catalyst and process for selectively hydrogenating ethylene in the presence of propylene utilizing a zeolite in conjunction with a hydrogenation metal is disclosed in U.S. Pat. No. 3,496,246. N. Y. Chen and P. B. Weisz in "Molecular Engineering of Shape-Selective Catalysts", Kinetics and Catalysis, Chem. Eng. Prog. Symp. Serial No. 73, Vol. 63, 1967, p. 86, described a platinum catalyzed hydrogenation employing a phosphine-poisoned platinum-exchanged sodium mordenite zeolite.
An excellent summary of the art of metal loaded zeolite catalysts and shape selective catalysis is given in Zeolite Chemistry and Catalysts, J. A. Rabo, ed., ACS Monograph 171 (1976). Of particular interest is Chapter 10, "Catalytic Properties of Metal-Containing Zeolites" by K. M. Minachev and Y. I. Isakov and Chapter 12, "Shape-Selective Catalysis" by S. M. Csicsery, the entire contents of which are herein incorporated by reference.
Heretofore, a shape selective metallic catalyst has not been prepared in which one metal function is incorporated into a zeolite characterized by a silica to alumina mole ratio of at least 12 and a constraint index, as hereinafter defined, in the approximate range of 1 to 12, e.g., ZSM-5 zeolite.